Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2016
Publication Date: 12/30/2016
Citation: Pounders, C.T., Sakhanokho, H.F. 2016. ‘Hapa White’, 'Hapa Pink', and 'Hapa Red' interspecific hybrid hibiscus cultivars. HortScience. 51(12):1616-1617. doi:10.21273/HORTSCI11291-16.

Interpretive Summary: 'Hapa White', 'Hapa Red', and 'Hapa Pink' are three new interspecific hibiscus cultivars developed at the USDA-ARS Thad Cochran Southern Horticultural Laboratory, Poplarville, MS. Plants of 'Hapa White', 'Hapa Red', and 'Hapa Pink' develop rapidly in containers with ultimate plant size dependent on container volume and environmental conditions with plants in a #3 nursery pot growing to 0.5 meters high x 0.3 meters wide from a liner within 3 months under optimum conditions. Under landscape conditions, plants should mature to approximately 1.5 meters high x 1.5 meters wide with minimal care. Plants of 'Hapa White', 'Hapa Red', and 'Hapa Pink' die to ground level each winter when subjected to freezing temperatures building a large multi-stemmed clump after several seasons of regrowth. Plants start flowering in late June. The three hibiscus cultivars are well suited to a variety of landscape uses such as a specimen plant, a color accent in shrub borders, a contrast plant in mixed landscape plantings or as a flowering plant in living screens. Plants perform best in full sun with moderate moisture and fertility. Their broad environmental adaptation and tolerance of common insects and diseases make them ideal plants for low maintenance plantings. Plants of 'Hapa White', 'Hapa Red', and 'Hapa Pink' are generally pest free, moderately vigorous with a spreading upright growth habit and white flowers. In cold hardiness zones 7 and 8, plants die to the ground in winter, developing a strong root system that regenerates tops each spring. The three selections are easily propagated by softwood stem or branched-shoot cuttings treated with 1500 ppm IBA under intermittent misting systems. The best rooting material should be taken from actively growing stock plants.

Technical Abstract: Hibiscus mutabilis, also known as confederate rose, is native to southeastern China, but it is also grown as an ornamental throughout the southeastern United States and is hardy in USDA zone 7 to 9. It is popular for its large, soft, gray-green foliage during the summer, and large, showy flowers produced late in the season when few other plants are in bloom. Hibiscus moscheutos and closely associated species of section Trionum are native to the eastern half of the US. Hybrids of these American species are widely available because they are winter hardy in much of the eastern US, and have attractive, tropical-looking flowers. Examples of artificial hybridization between H. mutabilis and the endemic North American species in Trionum section such as H. coccineum and H. moscheutos have been reported, but the resulting F1 plants were seed sterile. The goal of the hybridization efforts at the USDA-ARS Thad Cochran Southern Horticultural Laboratory in Poplarville, MS was to develop hibiscus cultivars with improved garden performance, reduced plant height, improved biotic and abiotic stress resistance, and prolific production of flowers of diverse colors. To that end, two Hibiscus species, H. moscheutos and H. mutabilis, and as a result, three cold hardy cultivars, 'Hapa White', 'Hapa Pink', and 'Hapa Red', have been released from this research. These cultivars are interspecific hybrids with white, red, and pink flowers that thrive in diverse landscape environments (USDA Cold Hardiness Zones 7-9). The three cultivars all bloom over an extended season as compared to the parental species. This extended flowering is due in part to the clones being sterile, setting neither seed nor seed pods. Growers which have evaluated the three releases report that overwintering losses are reduced and spring vigor is improved as compared to their traditional crops of H. mutabilis hybrids in the same environment.